SU1640626A1 - Method of determination of degree of polymerization of composite materials - Google Patents

Description

one

(21) 4450396/28

(22) 06/27/88

(46) 04/07/91. Bul № 13

(72) V.G. Orzaev and K.E. Nikitin

(53) 620.179.16 (088.8)

(56) Nosov V.A. Designing ultrasonic measuring equipment. M .: Mashinostroenie, 1472, s, 177-183. USSR author's certificate

 917073, cl. G 01 N 29/00, 1980

i

(54) METHOD FOR DETERMINING THE DEGREE OF POLYMERIZATION OF COMPOSITION MATERIALS

, (57) The invention relates to the ultrasonic testing of products and can be used to determine the degree of polymerization of composite materials in the process of forming products. The purpose of the invention is to improve the accuracy and informativeness by determining the degree of polymerization at the final stage of curing - The controlled product from the beginning of the formation is heard by ultrasonic vibrations and determine the changes in speed and attenuation coefficient, and in the final stage, when the dependence of speed and attenuation coefficient on the duration of polymerization The constant value of the monitored product is sounded by short ultrasonic pulses and the spectrum of the signal passed through from Elie, on which is judged on the extent and quality of the products polimerazatsii.

"

The invention relates to the ultrasonic testing of products and can be used to determine the degree of polymerization of composite materials in the process of forming articles for predominantly thin-walled.

The purpose of the invention is to improve the accuracy and information content by determining the degree of polymerization in the final stage of curing.

The essence of the invention is that the controlled product, from the beginning of the molding, sounds by ultrasonic vibrations and determines the change in speed and coefficient of extinction during the entire technological process, from the plastic state of the material to its curing -. In the final stage, when the dependences of the speed and attenuation coefficient on the duration of polymerization are constant, the product being monitored is sounded with short ultrasonic pulses, the spectrum of the signal passed through the product is measured, which determines the degree of polymerization and the quality of the product.

The method for determining the degree of polymerization of composite materials is as follows.

The controlled product is sounded by ultrasonic pulses with a filling frequency of 2 MHz, since at frequencies greater than 2.5 MHz, a strong absorption of ultrasound is observed, especially when the binder finds ™ with a flowing state and signal

ys

it is difficult to register, and for frequencies below 1 MHz, the sample thickness is small, which introduces a large error in determining the acoustic parameters. The duration of the ultrasonic pulse is selected from the condition of not less than 10 and not more than 15 oscillations per pulse, in this case from 5 to 10 ms.

The time of a single pulse passing through the product and amplitude is periodically measured during the entire molding time, taking into account the thickness of the product, the change in speed and absorption coefficient of the transmitted acoustic wave is determined, and the temperature and time dependences of the acoustic parameters obtained are determined at various technological conditions, from a highly elastic state to its curing. Upon reaching a constant value of the speed and absorption coefficient of ultrasound, short pulses are passed through the product using the same piezo emitters and piezo receivers, and the spectrum of the signal passed through the product is recorded. The ultrasonic pulses, when used at 2 MHz, are 0.5 ms long and can be obtained -the method of compensation of free oscillations of a piezo-vibrator.

For example, samples of prepregs based on CBM fabric or carbon tapes, fed with epoxy binder, were placed in several layers 5 mm thick for carbon fiber and 2. mm for organoplastic and with a certain constant pressure MPa heated from 20 to 125 ° C, measure simultaneously the change in acoustic characteristics. Taking into account the change in the sample thickness during the molding process,

The change in the velocity and the coefficient after the achievement of the constant values of the Absorption Absorption of the ultrasonic vibrations passing through the sample was determined. The frequency of ultrasonic oscillations in a pulse was 2 MHz. Upon reaching the desired molding temperature, the dependence of the change in acoustic characteristics (speed and absorption coefficient) on time was removed. After 3 hours from the beginning of the molding, - when these acoustic characteristics in the curing mode were assumed to be a constant value (for example, additional ultrasonic pulses without filling, which are equal to or less than half, emit and pass through the material that passed through the ultrasound vibrations and ultrasonic oscillation speeds. the frequency of filling the main ultrasonic pulses, and measure the spectral components of the received ultrasonic pulses, which are taken into account when determining the degree of polymerisation rial

ten

15

20

Q 5

leplasty with ultrasound speed of 2300 m / s, and for organoplastic 1800 m / s), short ultrasonic pulses equal in duration to 0.5 ms were sent through the sample. At the same time, a change in the spectral components of the acoustic signal transmitted through the material was observed. After 1.5 hours thereafter, a constant in time constant spectrum of the received pulse was recorded, which indicated that the binder in the material had polymerized. When a sample of these two samples was taken and extracted, it turned out that the degree of curing reached 98% for organoplastic and 98.5% for carbon plastic.

Thus, the measurement of the spectral components of the signal passing through the material increases the information about the processes of molding polymeric materials and allows determining the degree of polymerization of composite materials with greater accuracy.

Claims (1)

Invention Formula The method of determining the degree of polymerization of composite materials, which consists in the fact that from the beginning of the molding to curing the material, ultrasonic vibrations passed through the material are emitted and received, and the attenuation and velocity of ultrasonic vibrations are measured, taking into account the degree of polymerization of the material, in order to increase accuracy and informativeness by determining the degree of polymerization in the final stage of curing, the radiation is carried out by ultrasound pulses with charts. and 1.0-2.5 MHz and a duration of 10-15 oscillation periods, after reaching a constant value the attenuation and speeds of ultrasonic vibrations emit additional material ultrasonic pulses that pass through the material without duration, the duration of which is equal to or less than half the filling frequency of the main ultrasonic pulses, and measure the spectral components of the received ultrasonic pulses that are taken into account when determining the degree of polymerisation of the material.